The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Dense Wavelength-Division Multiplexing (DWDM) technology has become a dominant technology used in both long-haul and regional backbone transmission networks, and is gradually being introduced into Metropolitan Area Network (MAN). Conventional DWDM systems adopt separate encapsulation, i.e. fabricating linecards dedicated for one or more optical devices, and the linecards are inter-connected by fibers.
With developments in the technology, prices of optical devices are decreasing continuously. The cost of encapsulating an optical device typically remains high, and has become a bottleneck keeping the cost of the whole optical device high. Taking a laser as an example, the core of the laser may cost only several dollars, while the encapsulation may cost hundreds of dollars.
During the past few years, people have made efforts to integrate several optical devices, such as lasers and modulators on one semiconductor substrate to eliminate the cost generated by encapsulating each optical device separately. Meanwhile, the volumes of sub-modules, e.g. sub-modules for transmitting, receiving and monitoring in a DWDM system, are greatly reduced due to the reduction in encapsulation.
An optoelectronic integrated circuit is an apparatus in which several optical devices are integrated on a semiconductor substrate with corresponding periphery control circuits. FIG. 1 is a schematic diagram of the interior structure of an optoelectronic integrated apparatus at the transmitting end in accordance with the prior art. Referring to FIG. 1, in order to transmit information through an optoelectronic integrated circuit, the optoelectronic integrated apparatus at the transmitting end includes in its interior a top-layer control unit, a data switching unit, an optical source link control unit, n optical source links and n data channels corresponding to the n optical source links, and a wavelength combining unit, in which the “n” refers to the number of optical source links or data channels. FIG. 2 is a schematic diagram illustrating the data transmission using the data channels and the optical source links at the transmitting end of the optoelectronic integrated apparatus in the prior art. Referring to FIGS. 1 and 2, in practical service applications, each optical source link mainly includes an optical source and a modulator, and may also includes an optical link wiretapping (Tap) module. A link checking circuit in the optical source link control unit checks the performance of each optical source link by use of each corresponding Tap module, so that the optical source link control unit can adjust the optical source link suitably according to the result of checking, e.g. adjust the optical power in the optical source link. FIG. 3 is a schematic diagram illustrating a structure of the optoelectronic integrated apparatus at the receiving end in the prior art. Referring to FIG. 3, the optoelectronic integrated apparatus at the receiving end mainly includes in its interior a wavelength de-combining unit, n optical receiving units and an electric data processing unit.
When the optoelectronic integrated apparatus at the transmitting end is in operation, the optical source in an optical source link generates and outputs an optical signal to the modulator, and a corresponding data channel outputs an electric signal to the modulator. The modulator then modulates the received optical signal and the electric signal to generate and output an optical signal to the wavelength combining unit. The wavelength combining unit combines the optical signals received from all the optical source links and then outputs the combined optical signals to the optoelectronic integrated apparatus at the receiving end. In the optoelectronic integrated apparatus at the receiving end, the wavelength de-combining unit de-combines the received optical signals and outputs the de-combined n-way optical signals to the corresponding optical receiving units respectively, and each optical receiving unit converts a received optical signal into an electric signal and then outputs the electric signal to the electric data processing unit. Then the electric data processing unit processes the electric signals according to a certain service processing procedure.
At present, optical signals are of many advantages over electric signals in information delivering, such as enhanced capability of anti-interference, higher transmission speed, and etc. Therefore, the optoelectronic integrated apparatus has been used widely.
There are presently, however, no effective protecting measures for the optoelectronic integrated apparatus at the moment. Each optical source link may be used as a working link for transmitting service data. Thereby, when a failure, e.g., an optical source fails to emit light or a modulator malfunctions, occurs in any optical source link in an optoelectronic integrated apparatus, the whole optoelectronic integrated apparatus can not function properly, and thus the reliability of the optoelectronic integrated apparatus is impaired. In order to restore the working of the optoelectronic integrated apparatus, measures such as replacement, should be adopted in the prior art. However, because the components of each optical source link in an optoelectronic integrated apparatus are integrated on the same substrate and are encapsulated along with all the others, the faulty optical source link can not be replaced individually. As a result, the whole optoelectronic integrated circuit has to be replaced, which increases the maintenance and repair cost greatly.